Method and machine for rolling threads or the like

ABSTRACT

Round blanks consisting of ductile metallic material are formed with threads, knurled or otherwise profiled in a rolling machine wherein a head supports two or more cylindrical dies each having a flat and a profile including a first section of gradually increasing radius, a second section of constant radius and a third section of gradually decreasing radius. The head may rotate about a non-rotating blank so that the dies orbit about the blank, or the blank may rotate about its axis with respect to a stationary head. The flats of the dies face the periphery of the blank when the head is moved to operative position by the slide of a machine tool, and the dies are thereupon caused to turn so as to move the first sections of their profiles into frictional engagement with the blank. The rolling operation is completed when each of the dies completes a single revolution. The rotary movements of dies are synchronized by a gear train whose gears can lock the dies in selected angular positions so that the flats face a blank during movement of the head to or from the operative position. The gears can be unlocked in automatic response to movement of the head to operative position and are relocked as soon as the dies complete a single revolution.

ilnited States Patent [1 1 Kruse Oct. 21, 1975 METHOD AND MACHINE FORROLLING THREADS OR THE LIKE [76] Inventor: Werner Kruse, Waldhuterweg 5,

2053 Schwarzenbek, Germany 22 Filed: July 15, 1974 21 Appl. No.: 487,947

[30] Foreign Application Priority Data Primary Examiner-Lowell-A. LarsonAttorney, Agent, or FirmMichael S. Striker [57] ABSTRACT Roundblanksconsisting of ductile metallic material are formed with threads, knurledor otherwise profiled in a rolling machine wherein a head supports twoor more cylindrical dies each having a flat and a profile including afirst section of gradually increasing radius, a second section ofconstant radius and a third section of gradually decreasing radius. Thehead may rotate about a non-rotating blank so that the dies orbit aboutthe blank, or the blank may rotate about its axis with respect to astationary head. The flats of the dies face the periphery of the blankwhen the head is moved to operative position by the slide of a machinetool, and the dies are thereupon caused to turn so as to move the firstsections of their profiles into frictional engagement with the blank.The rolling operation is completed when each of the dies completes asingle revolution. The rotary movements of dies are synchronized by agear train whose gears can lock the dies in selected angular positionsso that the flats face a blank during movement of the head to or fromthe operative position. The gears can be unlocked in automatic responseto movement of the head to operative position and are relocked as soonas the dies complete a single revolution.

31 Claims, 10 Drawing Figures US. Patent Oct. 21, 1975 Sheet30f6 I3,913,365

US. Patent 061;. 21, 1975 Sheet 4 of6 3,13,5

US Patent Oct. 21, 1975 Sheet5 of6 3,913,365

U.S. Patsm Oct. 21, 1975 Sheet 6 of6 3,3,35

METHOD AND MACHINE FOR ROLLING THREADS OR THE LIKE BACKGROUND OF THEINVENTION The present invention relates to improvements in methods andmachines for cold forming round workpieces, and more particularly to animproved method and machine for rolling (e.g., threading, knurling,ridging, grooving or burnishing) profiles into peripheral surfaces ofround workpieces, especially workpieces which consist of ductilemetallic material. Still more particularly, the invention relates toimprovements in a method and machine for rolling threads or analogousprofiles into round workpieces by resorting to a plurality ofsubstantially cylindrical dies whose profiles are complementary to thedesired profile ofa round workpiece.

It is already known to roll threads by resorting to machines whichemploy two or more cylindrical dies and utilize a gear train whichinsures that all of the dies rotate in synchronism with each other. Thedies are mounted in a head which is movable tangentially of a blank andmaintains the dies in spaced-apart positions so that the distancesbetween neighboring dies equal the root diameter of threads on afinished workpiece. In order to move the dies into proper engagementwith a blank, the head must be moved in a first direction at rightangles to the axis of the blank and is thereupon retracted, again atright angles to the axis of the blank but in the opposite direction,when the thread rolling operation is completed.

THe versatility of thread rolling machines which utilize the justdescribed heat is rather limited, especially because the length ofintervals which are required for the profiling of a blank is excessive,at least for the purpose of mass production. As a rule, the blank mustcomplete l5-20 revolutions during profiling, and the disengagement ofdies from the finished workpiece requires an interval corresponding tothat which elapses while the workpiece completes about five additionalrevolutions. Moreover, the just discussed head can be mounted only inspecially designed thread rolling ma chines, i.e., the head cannot beused in conventional turning lathes, chucking automatics, bar machinesor analogous machine tools. This is due to the fact that such machinetools are incapable of invariably feeding and withdrawing the head whilethe respective blanks complete between and revolutions. The number ofrevolutions of a workpiece during engagement with thread rolling diescannot be selected at will because the number of revolutions determinesthe quality of the thread or another profile which is produced in theperipheral surface of a blank during engagement with cylindrical dies.Moreover, the just discussed head must move the dies into and fromengagement with a blank by exertion of a considerable force which,depending on the dimensions of the head and the nature of threads, oftenapproaches and even exceeds 1,000 kp.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved method of providing round blanks which consist of aductile metallic material with threads or analogous profiles with a highdegree of reproducibility, within intervals of time which are shorterthan those required in accordance with heretofore known methods, and byresorting to relatively simple rolling dies.

Another object of the invention is to provide a method according towhich the movements of dies into engagement with round blanks or viceversa necessitate the exertion of relatively small forces.

A further object of the invention is to provide a novel and improvedrolling machine wherein the head for two or more cylindrical rollingdies is constructed, assembled and movable in a novel and improved way.

An additional object of the invention is to provide a machine wherein asingle revolution of each of two or more substantially cylindrical diessuffices to complete the formation of threads or analogous profiles onround metallic blanks.

A further object of the invention is to provide the machine with noveland improved means for moving the dies into a requisite position withrespect to a blank and/or vice versa.

Another object of the invention is to provide a novel and improved headfor two or more cylindrical rolling dies which can be installed inconventional machine tools, such as turning lathes, chucking automatics,bar machines or the like.

Still another object of the invention is to provide novel dies for usein the improved machine.

A further object of the invention is to provide a machine which iscapable of properly profiling relatively soft as well as relatively hardblanks and wherein the conversion from treatment of softer blanks totreatment of harder blanks or vice versa takes up a minimum of time.

The method of the present invention can be practiced to roll threads oranalogous profiles into the peripheral surfaces of round blanks whichconsist of a ductile material and which are treated by two or morecylindrical dies having profiles which are complementary to the desiredprofile ofa blank. The method comprises the steps of positioning thedies into frictional contact with a selected portion of the peripheralsurface of a round blank while maintaining the axes of the dies atidentical distances from the axis of the blank, and rotating the blankabout its axis or orbiting the dies about the axis of the blank so thatthe dies rotate about their respective axes due to frictional engagementwith the blank and complete the rolling of a profile into the peripheralsurface of the blank in response to completion of one revolution abouttheir respective axes.

The method preferably further comprises the steps of locking the diesagainst rotation about their respective axes prior to the positioningstep and locking the dies against rotation about their respetive axesupon completion of the one revolution, i.e., immediately following thecompleted profiling of a blank.

Still further, the method may comprise the step of biasing the dies topredetermined angular positions which the dies assume upon disengagementof their profiles from a profiled blank.

The method may also comprise the steps of moving a blank to apredetermined position relative to the dies or vice versa, andterminating the first locking step in the course of the moving step. Forexample, the dies can be moved relative to a rotating blank and areunlocked during such movement so that they can begin to turn under theaction of one or more springs in order to frictionally engage a blankwhereby the dies begin to rotate about their axes due to rotation of theblank or because a holder for the dies orbits about the axis of theblank. The second locking step is preferably carried out in automaticresponse to completion of one revolution, i.e., in response to completedprofiling of a blank.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved machine itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic plan view of ahead which can be used in a two-die cylindrical die rolling machine;

.FIG. 2 is a sectional view as seen in the direction of arrows from theline IIII of FIG. 1;

FIG. 3 is a sectional view as seen in the direction of arrows from theline III-III of FIG. 2;

FIG. 4 is a sectional view as seen in the direction of arrows from theline IVIV of FIG. 3;

FIG. 5 is an enlarged fragmentary plan view as seen in the direction ofarrow A in FIG. 4;

FIG. 6 is an end elevational view of a die;

FIG. 7 is an axial sectional view of a die;

FIG. 8 is a fragmentary plan view of a machine which can utilize thehead of FIG. 1;

FIG. 9 is a sectional view of a head which can be utilized in athree-die cylindrical die rolling machine; and

FIG. 10 is an end elevational view of a portion of the head as seen inthe direction of arrow X in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 8 show certaindetails of a two-die cylindrical die rolling machine having a rollinghead 1 including two substantially cylindrical dies 4 and 5. The head 1is movable radially of a rotating round blank 2 which is to be formedwith threads, knurled, grooved, burnished and/or similarly profiled. Thehead 1 includes a bifurcated holder 3 wherein the dies 4, 5 arerotatably mounted on eccentric portions of studs 13,

14. The dies 4, 5 can rotate in unison due to the provision ofa geartrain having gears 10, 6 which are respectively coaxial and rigid withthe dies 4, 5 gears 9, 7 which respectively mesh with the gears 10, 6,and a fifth gear 8 which meshes with the gears 7, 9. As shown in FIGS.1, 6 and 7, each of the dies 4, 5 has a flat l2 and a profile 11 whichincludes a first section 11a extending along an arc of approximately225, a second section 11b extending along an arc of approximately 90,and a third section 110 extending along an arc of approximately 45. Theradius of the section 11a increases gradually contrary to the directionin which the die 4 or 5 rotates (see the arrow a); the radius of thesection 11b is constant; and the radius of the section 110 decreasescontrary to the direction of rotation. The flat 12 extends in part intothe section 11a and in part into the section 11c.

The flats 12 of the dies 4, 5 are parallel to and face each other in thestarting angular positions of the dies. The distance between these flatsin the starting positions of the dies is slightly greater than themaximum diameter of a finished workpiece. As known, the diameter of theworkpiece 2 increases during rolling because some material of theworkpiece penetrates into the grooves of the threaded portions 11. Sincethe distance between the flats 12 (when the flats assume the positionsshown in FIG. 1) is greater than the diameters of the crests of threadswhich are rolled into the workpiece 2, the head 1 can be readilywithdrawn from the operative position shown in FIG. 1 by moving in adirection to the right. The movement of the head 1 back to the positionshown in FIG. 1 presents no problems since the diameter of an untreatedworkpiece 2 is evidently less than the distance between the flats 12when the flats are maintained in parallelism with and face each other.

The gears 7 and 9 which respectively mesh with the gears 6 and 10 of thedies 5 and 4 have radial projections or lobes 17, 18 which constitutecomponent parts of two detent devices. The detect device which includesthe lobe 17 further includes a reciprocable locking bolt 20 and a spring22 which biases the bolt 20 in a direction to the left, as viewed inFIG. 1. The detent device including the lobe 18 further comprises areciprocable locking bolt 21 and a helical spring 23 which is strongerthan the spring 22 and urges the bolt 21 in a direction to the left, asviewed in FIG. 1. The locking bolts 20, 21 are articulately connectedwith the respective arms of a two-armed actuating lever 19 which ispivotable on a pin 33 mounted in the holder 3. The recess or notch 20awhich receives the rounded end portion of the lower arm of the actuatinglever 19, as viewed in FIG. 1, is longer than the notch 21a, i.e., thelocking bolt 20 has a certain amount of freedom of lengthwise movementrelative to the actuating lever 19 and locking bolt 21. The front endportion 21b of the locking bolt 21 is narrower than the front endportion 20b of the locking bolt 20.

The median gear 8 of the gear train 6-10 has an eccentric post 25 whichis connected with one end of a helical resetting spring 24 (seeparticlarly FIG. 4). The other end of the spring 25 is attached to apost 24a in the holder 3. The purpose of the spring 24 is to permanentlybias the gears 7, 9 in directions to move the lobe 17 against the endportion 20b of the locking bolt 20 and/or to move the lobe 18 of thegear 9 into abutment with the end portion 21b of the locking bolt 21.When the lobe l8 abuts against the end portion 21b of the locking bolt21, the dies 4 and 5 assume the starting positions shown in FIG. 1,i.e., the flats 12 are then parallel to and face each other.

FIG. 8 shows a portion of a turning machine 28 having a rotary holder orchuck 29 for a cylindrical workpiece 2. The head 1 (i.e., the holder 3)is mounted on a cross slide 26 which is movable on a main slide 27 indirections indicated by arrows b and c. The main slide 27 is movable inthe bed B of the machine tool 28 in the axial direction of the workpiece2. The front end face of the workpiece abuts against a center 30a whichis mounted in a tailstock 30. The tailstock 30 further carries a trip 31which extends into the path of movement ofa handle 32 rigid with andturnable with the pin 33 for the actuating lever 19 (see also FIGS. 4and 5). When the cross slide 26 is shifted in the direction indicated byarrow b (FIG. 8), the handle 32 is engaged and pivoted by the trip 31 sothat the actuating lever 19 pivots clockwise, as viewed in FIG. 1, andretracts the end portion 21b of the locking bolt 21 from engagement withthe lobe 18 of the gear 9. The spring 24 then turns the gear 8 whichrotates the gears 7, 9 and hence the gears 6, 10 whereby the sections 11a of the dies 4, 5 engage the rotating workpiece 2 and the dies 4, 5are rotated due to frictional engagement with the work. The threadrolling operation is completed when each of the dies 4, 5 completes asingle revolution. The dies are then automatically locked in theirstarting positions so that the head 1 can be withdrawn (arrow in FIG.8),

the finished workpiece removed, and a fresh blank 2 inserted into theholder or chuck 29 before the cross slide 26 is again caused to move inthe direction indicated by arrow b.

The handle 32 is automatically disengaged from the trip 31 when thecross slide 26 is retracted (arrow 0) whereby the spring 23 (which isstronger than the spring 22) expands and pushes the locking bolt 21 intothe path of the lobe 18 on the gear 9.

The operation is as follows:

When the cross slide 26 is retracted, the dies 4 and 5 assume thestarting angular positions shown in FIG. 1. The end portion 21b of thelocking bolt 21 engages the lobe 18 of the gear 9 to insure that theflats 12 are maintained in parallelism with and face each other. Thespring 24 is stressed (see the angular position of the post 25 inFIG. 1) and tends to rotate the gear 8 in a counterclockwise direction,as viewed in FIG. 1.

The slide 26 is thereupon moved in the direction of arrow b (FIG. 8)whereby the handle 32 strikes against the trip 31 on the tailstock andpivots the actuating lever 19 clockwise, as viewed in FIG. 1. Thus, the

spring 24 is free to rotate the gear 8 counterclockwise at a time whenthe flats 12 of the dies 4, 5 are located at the opposite sides of therotating blank 2. The gear 8 rotates the gears 7, 9 clockwise and thegears 7, 9 totate the gears 6, 10 and dies 5, 4 counterclockwise.Consequently, the sections 1 1a of the profiles 1 l on the dies 4, 5come into engagement with the peripheral surface of the blank 2 and thedies 4, 5 begin to rotate due to frictional engagement with the blankwhich is driven by the chuck 29. The angular position of the actuatinglever 19 due to engagement between the trip 31 and handle 32 is suchthat the locking bolts 20, 21 cannot interfere with rotary movements ofthe respective gears 7 and 9. The rolling operation is completed inresponse to rotation of the dies 4, 5 through 360, i.e., at a time whenthe flats 12 are again parallel to and face each other.

As mentioned above, the width of the end portion 21a of the locking bolt21 is somewhat less than the width of the end portion 20b of the lockingbolt 20. When the locking bolt 21 is withdrawn by the actuating lever 19due to engagement between the trip 31 and handle 32, the end portion 20bof the locking bolt 20 is free to move under the action of therelatively weak spring 22 and engages the end face of the lobe 17 on therotating gear 7. Thus, the locking bolt 20 does not prevent rotation ofthe gear 7. Once the lobe 17 moves beyond the end portion 20b, thespring 22 expands further and moves the end portion 20b behind the lobe17. Consequently, the end portion 20b automatically arrests the gear 7(and hence the gears 4, 8, 9, 10 and dies 4, 5) when the gear 7practically completes a full revolution, i.e., when the rollingoperation is completed. The end portion 21b of the locking bolt 21remains in retracted or inoperative position because the handle 32 isstill in engagement with the trip 31.

While the gear 8 rotates due to frictional engagement between therotating blank 2 and the dies 4, 5, the spring 24 dissipates energyduring the first stage of rotation and thereupon again stores energy asthe lobe 17 approaches the end portion 20b of the locking bolt 20 whichis held in the extended or operative position. When the cross slide 26is thereupon retracted (arrow 0 in FIG. 8) and the handle 32 isdisengaged from the trip 31, the relatively strong spring 23 pushes thelocking bolt 21 to its extended position and the spring 24 contracts tothe extent which is necessary to move the lobe 18 of the gear 9 intoengagement with the end portion 21b. The movement of locking bolt 21 tothe extended position of FIG. I automatically entails a retraction ofthe locking bolt 20. The extent of angular movement of the gear 8 underthe action of spring 24 as a result of disengagement of handle 32 fromthe trip 31 corresponds to the difference between the widths of the endportions 20b and 21b. The finished workpiece is then accessible forremoval from the machine and a new blank 2 is inserted into the chuck 29before the cross slide 26 again moves in the direction of arrow b tostart the next rolling operation.

The studs 13, 14 for the dies 4, 5 are held in selected angularpositions by arresting screws 34, 35 (see FIG. 3). When the screw 34 or35 is loosened, the angular position of the respective stud can bechanged and the screw 34, 35 is thereupon tightened to cause therespective prongs 3a, 3b or 3c, 3d of the holder 3 to frictionallyengage and hold the respective stud in the selected angular position.The angular adjustment of studs 13, 14 results in movement of the axesof dies 4, 5 toward or away from each other. This is necessary when abatch of blanks 2 consisting of a relatively soft material is followedby a batch of harder blanks which cause a more pronounced spreading ofthe two legs 3A, 3B of the holder 3 when .the dies 4, 5 rotate with arelatively hard blank.

It is clear that the head 1 of FIGS. 1 to 8 can carry more than two (forexample, three) substantially cylindrical dies.

An important advantage of automatic locking of the dies 4, 5 in theirstarting positions upon completion of a rolling operation is that thecross slide 26 can be fed forwardly (arrow b) as well as retracted(arrow 0) by a programming system because the length of the intervalwhich is needed for the rolling of threads or the like on a blank 2 isalways the same. Thus, the operator need not observe the angularpositions of the uies 4, 5 before the cross slide 26 is retracted inorder to move the dies 4, 5 away from the finished workpiece. A rollingoperation can be completed with a small fraction of a second.

The configuration of the sections 11a of the profile 11 on a die 4 or 5can be selected as follows:

The radii of roots and crests and the inclination of flanks or threadson the section 11a can increase gradually contrary to the directionindicated by arrow 0 (FIG. 6).

The radii of roots and the inclination of flanks are constant, the sameas in the section 11b, but the radii of crests increase gradually fromthe flat 12 toward the section 11b. Thus, the height of the profile ofthreads on the section 11a increases gradually toward the height ofprofile on the section 11b.

The increase in the radii of roots and the increase in inclination offlanks are less pronounced than the increase in the radii of crests.This, too, insures that the depth of grooves increases gradually towardthe full depth of grooves in the section 11b.

FIGS. 9 and 10 illustrate a head 101 which forms part of a three-diecylindrical-die rolling machine. The head 101 includes threesubstantially cylindrical dies 104 each of which may be configurated ina manner as described in connection with the dies 4 and '5. The dies 104are equally spaced from each other and are rotatable in a holderincluding two parallel plates 103, 103. Each of the dies 104 isrotatable with a coaxial gear 106, and the three gears 106 mesh with acentrally located intermediate gear 108. The flats of the dies 104 areshown at 112. The first section of the profile on each die 104(corresponding to the section 11a in FIG. 6) extends along an arc of 180(as considered from the center of the respective flat 112); the secondsection extends along an arc of 90, and the third or receding sectionalso extends along an arc of 90.

The gear 108 is a functional equivalent of the gear 8 and carries aprojection or lobe 117 which can cooperate with two locking bolts 120,121. The locking bolts 120, 121 are respectively biased by springs 122,123 and can be moved lengthwise by one arm ofa pivotable actuating lever119 the other arm of which constitutes a handle 132. The spring 123 isstronger than the spring 122. The gear 108 has an eccentrically mountedpost 125 which is connected to one end ofa helical restoring spring 124.The latter serves to maintain the dies 104 in their starting positionsin which the flats l 12 face the adjacent portions of the peripheralsurface of a rotary blank which extends into the space between the dies104.

FIG. 9 shows that the portion of the lobe 117 which can be engaged bythe locking bolt 122 extends beyond the portion which is to be engagedby the locking bolt 121. This insures that the locking of gear 108 bythe bolt 120 is slightly delayed when the actuating lever 119 disengagesthe locking bolt 121.

The dies 104 are mounted on eccentric portions of studs 115 each ofwhich is rigid with a discrete gear 161. The gears 161 mesh with a ringgear or internal gear 162 to thus insure that the angular adjustment ofone stud 115 invariably entails an equal angular adjustment of the othertwo studs 115. All of the studs 115 can be adjusted simultaneously bychanging the angular position of the internal gear 162 in the head 101.The gear 162 can be turned in the head 101 in response to loosening oftwo nuts 163 shown in FIG. 10. Adjustments of the angular positions ofstuds 115 via gears 162, 161 do not change the spacing between the dies104, as considered in the circumferential direction of the gear 162 andthe distance between the axis of the gear 162 and the axes of the dies104 invariably changes to the same extent.

The operation of the machine which utilizes the head 101 of FIGS. 9 and10 is as follows:

The head 101 has a flange 160 which can be mounted on the main slide ofa turning machine. The axis of the gear 162 must coincide exactly withthe axis of a rotating blank (not shown) which can be mounted in arotary holder similar or analogous to the chuck 29 of FIG. 8. The head101 is thereupon moved axially so that the flats 112 of the dies 104 areadjacent to a selected portion of the peripheral surface on the rotatingblank, namely that portion which is to be knurled, threaded or otherwiseprofiled (depending on the configuration of the sections of the profilesof the dies 104). The main slide of the machine can be moved by aprogramming system and is arrested when a trip (similar to the trip 31of FIG. 8) engages the handle 132 of the actuating lever 119. The latterdisengages the locking bolt 121 from the lobe 117 of the gear 108 sothat the spring 124 is free to dissipate energy and rotates the gears106 and dies 104 clockwise. as viewed in FIG. 9 and 10. This moves thefirst sections of the dies 104 into engagement with the rotating blank.From there on, the dies 104 rotate due to frictional engagement with thedriven blank and the latter is formed with a profile which iscomplementary to the profiles of the second sections of the dies 104.

The spring 124 dissipates energy during the first stage ofcounterclockwise rotation of the gear 108 and thereupon stores energy asthe pin moves counterclockwise beyond the six oclock position, as viewedin FIG. 10. When the gear 108 completes a revolution, the lobe 117strikes against the locking bolt 120 or 121 and arrests the dies 104 insuch angular positions in which the flats 1 12 again face the adjacentportions of the peripheral surface of the finished workpiece. Thus, thehead 10] can be withdrawn by moving axially of the workpiece, i.e., in adirection to the right, as viewed in FIG. 9.

It is equally within the purview of the invention to omit theaforementioned trip and to manually pivot the actuating lever 119through the medium of the handle 132 when the dies 104 are disposedaround a selected portion of the peripheral surface of a rotating blank.The rolling operation is the same as described above and the head 101can be retracted axially of the finished workpiece by an automaticmechanism which is set in operation with a predetermined delay followingmanual actuation of the handle 132. The rolling operation is completedwithin a fraction of a second and normally requires only a fewrevolutions of the blank, i.e., a number of blank revolutionscorresponding to a full revolution of each of the dies 104.

The machine which utilizes the head 101 of FIGS. 9

and 10 can be modified as follows:

The flange can be secured to a rotary part (e.g., to the spindle) of aturning machine. The chuck or other holder means for the blank does notrotate and is held in such position that the axis of the blank coincideswith the axis of the number (spindle) which rotates the head 101. Thehead 101 is preferably held against axial movement but the blank ismovable axially so as to place a selected portion of its periphery intothe space between the flats 112 of the dies 104 which orbit about theaxis of the spindle. The actuating lever 119 is pivoted as soon as theblank reaches a desired axial position whereby the spring 124 causes thegear 108 to change the angular positions of the dies 104 in the holder103, 103' so that the profiled first sections of the dies engage theblank and the dies rotate about their axes while orbiting about thenon-rotating blank. The blank then acts not unlike a fixed sun gear in aplanetary transmission and the dies 104 act not unlike planet pinionwhich are rotatable in their carrier (103, 103') which rotates about thesun gear. If the head 101 is to rotate with a spindle or the like, itmay be provided with a-ring-shaped trip 164 which can be braked relativeto the rotating flange 160 to thereby pivot the actuating lever 119 sothat the latter can disengage the locking bolt 121 from the lobe 117 ofthe gear 108 to thus initiate a rolling operation. Such operation iscompleted automatically when the lobe 117 is engaged by the locking bolt120 whereby the flats 112 face the adjacent portions of the finishedworkpiece which can be withdrawn by moving it axially and in a directionto the left, as viewed in FIG. 9.

An important advantage of the improved method and apparatus is that thedies can be moved into an optimum position with respect to a blank (orvice versa) by exertion of a negligible force. This is attributable tothe provision of flats 12, 112 which enable the dies to assume theiroperative positions without even touching a blank. Also, the head 1 or101 can be mounted in a conventional machine tool (lathe, chuckingautomatic, bar machine or the like) without necessitating any or byrequiring minimal alterations of such machine tools (see the trip 31 inFIG. 8). Thus, when a head 1 of the type shown in FIGS. 1-7 is mountedin the machine tool 28 of FIG. 8, the cross force which is needed tomove the cross slide 26 into the illustrated position is an extremelysmall fraction of the force (up to 1,000 kp) which is needed to move aconventional head into proper engagement with a blank.

Another advantage of the improved method and machine is that, regardlessof whether the blank rotates about its axis or the dies orbit about theaxis of a nonrotating blank, the intervals which are required forprofiling are always of identical length so that the finished workpiececan be replaced with fresh blanks at regular intervals. Moreover, andsince the rolling operation is invariably completed in response to asingle revolution of the dies 4, 5 or 104, the finished workpiece cancontinue to rotate about its axis or the holder 103, 103 can continue toorbit about the axis of a finished workpiece without damaging theprofile of the finished product. This will be readily understood byconsidering that the dies have flats 12 or 112 and that the rotation ofdies about their respective axes is automatically terminated as soon aseach die in a head completes a single revolution. Such construction andmode of operation insure that the quality of profiles which are rolledinto blanks is not dependent on the conscientiousness and/or skill ofthe attendants; in fact, if the machine tool wherein the head 1 or 101is mounted is equipped or associated with automatic blank feeding andproduct removing devices, the operation may be automated to such anextent that a single attendant can supervise an entire battery ofmachine tools.

The head 1 or 101 can be used for rolling threads or analogous profilesinto extremely short workpieces, for rolling threads all the way to thecollar or flange of a round blank, for rolling threads with or withoutrunout, and also for rolling extremely short threads, as considered inthe axial direction of the blank.

The first sections of the profiles of dies 4, 5 or 104 (see the section11a in FIG. 6) have increasing radii in order to reduce wear on thedies, and the third sections (110) have decreasing radii in order toimprove the quality of profiles on finished articles, for example, bypreventing the formation of pronounced ridges or the like which developin responseto abrupt relaxation of pressure between a die and a blank.The length of sections 11a, 11b, 11c, as considered in thecircumferential direction of the dies depends on the ratio of diediameter to blank diameter, on the type of profiles of dies and/or onthe height of treads or other raised portions on the sections lla-IIc.As a rule, the section will extend along an arc of at least 180 and thesection 110 along an arc of less than 100. The section 11b may extendalong an arc of approximately 90 or less.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by letters Patent isset forth in the appended claims.

1. A method of rolling threads or analogous profiles into the peripheralsurfaces of ductile round blank means with die means including aplurality of substantially cylindrical dies having profiles which arecomplementary to the desired profiles of blanks, comprising the steps ofpositioning the dies into frictional contact with the peripheral surfaceof a blank means while maintaining the axes of the dies at identicaldistances from the axis of the blank means; rotating one of said meansrelative to the other about the axis of the blank means so that the diesrotate about their respective axes due to frictional engagement with theblank means and complete the rolling of a profile into the peripheralsurface of the blank means in response to completion of one revolutionabout their respective axes; and biasing said dies to predeterminedangular positions which said dies assume upon disengagement of theirprofiles from a profiled blank means.

2. A method of rolling threads or analogous profiles into the peripheralsurfaces of ductile round blank means with die means including aplurality of substantially cylindrical dies having profiles which arecomplementary to the desired profiles of blanks, comprising the steps ofpositioning the dies into frictional contact with the peripheral surfaceof a blank means while maintaining the axis of the dies at identicaldistances from the axis of the blank means; rotating one of said meansrelative to the other about the axis of the blank means so that the diesrotate about their respective axes due to the frictional engagement withthe blank means and complete the rolling of a profile into theperipheral surface of the blank means in response to completion of onerevolution about their respective axes; locking the dies againstrotation about their respective axes prior to said positioning step; andlocking said dies against rotation about their respective axes uponcompletion of said one revolution.

3. A method as defined in claim 2, further comprising the steps ofmoving a blank means into a predetermined position relative to thedies,or vice versa, and terminating the first locking step in the course ofsaid moving step.

4. A method as defined in claim 2, wherein said second locking step iseffected in response to completion of said one revolution.

5. In a machine for rolling threads or analogous profiles into theperipheral surfaces of ductile round blanks, a combination comprising afirst holder arranged to support a blank therein; a head including asecond holder, a plurality of spaced-apart substantially cylindricaldies rotatably mounted in said second holder and having profilescomplementary to the desired profile of a blank in said first holder, agear train mounted in said second holder and connecting said dies forrotation in synchronism with each other, means for moving the axes ofsaid dies nearer to or away from each other and comprisng shaftsturnably mounted in said second holder and having eccentric portionssurrounded by the respectivedies, one of said holders being movablerelative to the other holder to a predetermined position in which saiddies are adjacent to a selected portion of the peripheral surface of ablank in said first holder and the axes of said dies are disposed atidentical distances from the axis of such blank; and means for rotatingone of said holders about the axis of a blank in said first holderwhereby the blank and said second holder move relative to each otherabout the axis of the blank in said first holder and the dies completethe profiling of the blank in response to completion of one revolutionabout their respective axes owing to frictional engagement with theblank.

6. A combination as defined in claim 5, wherein the profile of each ofsaid dies comprises a section whose radius increases contrary to thedirection of rotation of the die about its axis during frictionalengagement with a blank is said first holder.

7. A combination as defined in claim 6, wherein said radius increasesgradually. A A

8. A combintion as defined in claim 6, wherein said section of theprofile of each of said dies has raised portions of uniform height.

9. A combination as defined in claim 6, wherein said section of theprofile of each of said dies has raised portions whose height increasescontrary to the direction of rotation of the respective die about itsaxis.

10. A combination as defined in claim 9, wherein the profile of each ofsaid dies has a second section which follows the respective firstmentioned section, as considered contrary to the direction of rotationof the corresponding die about its axis, and has a constant radius.

11. A combination as defined in claim 6, wherein the profile of each ofsaid dies has a flat which precedes said section, as considered in thedirection of rotation of the respective die about its axis, said flatbeing adjacent to and spaced from said selected portion of a blank insaid predetermined position of said one holder and said head furthercomprising means for rotating said dies about their respective axessufficiently to move said sections into frictional engagement with theblank in said first holder.

12. A combination as defined in claim 5, wherein the profile of each ofsaid dies has a first section whose radius increases contrary to thedirection of rotation of the respective die about its axis, a secondsection following said first section and having a constant radius, and athird section which follows said second section and whose radiusdecreases in said direction.

13. A combination as defined in claim 12, wherein each of said firstsections extends along an arc of at least l80, as considered in thecircumferential direction of the respective die.

14. A combination as defined in claim 12, wherein each of said secondsections extends along an arc of approximately 90", as considered in thecircumferential direction of the respective die.

15. A combination as defined in claim 12, wherein each of said thirdsections extends along an arc of less than 100, as considered in thecircumferential direction of the respective die.

16. In a machine for rolling threads or a nalogous profiles into theperipheral surfaces of ductile round blanks, a combination comprising afirst holder arranged to support a blank rotatable about its axis; a

head including a second holder, a plurality of spacedapart substantiallycylindrical dies rotatably mounted on said second holder and havingprofiles complementary to the desired profile ofa blank in said firstholder, and a gear train mounted in said second holder and connectingsaid dies for rotation in synchronism with each other, said head beingmovable relative to said first holder from a first to a second positionin which said dies are adjacent to a selected portion of the peripheralsurface of a blank in said first holder and the axes of said dies aredisposed at identical distances from each other; releasable lockingmeans for locking said dies, when said head is in said first position,in a predetermined angular relationship with respect to each other;means cooperating with said releasable locking means to automaticallyrelease the latter upon movement of said head from said first to saidsecond position; means operatively connected to said dies for moving thesame out of said predetermined angular position when said locking meansare released so that the dies engage the peripheral surface of a blankin said first holder; and means for rotating said first holder about theaxis of a blank in said first holder whereby said blank rotates withsaid first holder and the dies complete the profiling of the blank inresponse to completion of one revolution about their respective axesowing to frictional engagement with the blank.

17. A combination as defined in claim 16, wherein each of the dies has afiat, and wherein said flats are adjacent to but spaced from theperipheral surface of the blank in said predetermined angular positionof said dies.

18. In a machine for rolling threads or analogous profiles into theperipheral surfaces of ductile roung blanks, a combination comprising, afirst holder arranged to support a blank therein; a head including asecond holder, first and second spaced-apart substantially cylindricaldies rotatably mounted in said second holder and having profilescomplementary to the desired profile of the blank in said first holder,and each of said dies having a flat, said head further comprising meansfor rotating said dies about their respective axes to move the profilesof said dies in frictional engagement with the blank in said firstholder, a gear train mounted in said second holder and connecting saiddies for rotation in synchronism with each other, said gear trainincluding first and second gears coaxial and rigid with said first andsecond dies, third and fourth gears respectively mating with said firstand second gears, and additional gear means mating with said third andfourth gears, and detent means for releasably holding said dies againstrotation about their respective axes, said detent means comprising firstand second projections respectively provided on said third and fourthgears, first and second locking bolts movable into and out, of the pathof movement of said first and second projections, and actuating meansfor moving said bolts, one of said holders being movable relative tosaid other holder to a predetermined position in which said flats areadjacent to a selected portion of the peripheral surface of the blank insaid first holder and the axes of said dies are disposed at identicaldistances from the axis of such blank; and means for rotating one ofsaid holders about the axis of a blank in said first holder whereby theblank and the second holder move relative to each other about the axisof the blank in said first holder and the dies complete the profiling ofthe blank in response to completion of one revolution about theirrespective axes owing to frictional engagement with the blank.

19. A combination as defined in claim 18, wherein said detent meansfurther comprises discrete first and second resilient means for biasingsaid first and second locking bolts into the path of movement of therespective projections.

20. A combination as defined in claim 19, wherein the bias of said firstresilient means exceeds the bias of said second resilient means and saidactuating means is arranged to disengage one of said bolts from therespective projection when the other of said bolts extends into the pathof movement of the respective projection whereby said first resilientmeans automatically disengages said second bolt against the oppositionof said second biasing means when said actuating means allows said firstbolt to move into the path of movement of said first projection.

21. A combination as defined in claim 20, wherein said second lockingbolt is mounted in said second holder with limited freedom of movementrelative to said actuating means.

22. A combination as defined in claim 18, wherein said additional gearmeans comprises a fifth gear in mesh with said third and fourth gearsand said means for rotating said dies comprises resilient means arrangedto bias said fifth gear so that said fifth gear tends to rotate saiddies by way of said first to fourth gears when said detent means permitsrotation of said third and fourth gears, said resilient means beingarranged to bias said projections against the respective locking boltswhen said flats are adjacent to but spaced from a blank in said firstholder.

23. A combination as defined in claim 22, wherein said fifth gearcomprises an eccentric post and said resilient means comprises a springconnected to said post and reacting against said second holder.

24. In a machine for rolling threads or analogous profiles into theperipheral surfaces of ductile round blanks, a combination comprising afirst holder arranged to support a blank therein; a head including asecond holder, a plurality of spaced-apart substantially cylindricaldies rotatably mounted in said second holder and having profilescomplementary to the desired profile of a blank in said first holder,and a gear train mounted in said second holder and connecting said diesfor rotation in synchronism with each other, one of said holders beingmovable relative to the other holder to a predetermined position inwhich said dies are adjacent to a selected portion of the peripheralsur' face of a blank in said first holder and the axes of said dies aredisposed at identical distances from the axis of such blank; and amachine tool for rotating one of said holders about the axis of a blankin said first holder whereby the blank and the second holder moverelative to each other about the axis of the blank in said first holderand the dies complete the profiling of the blank in response tocompletion of one revolution about their respective axes owing tofrictional engagement with the blank, said dies having flats which areadjacent to but spaced from the blank in said first holder in saidpredetermined position of said one holder, and said head furthercomprising resilient means for rotating said dies about their respectiveaxes sufficiently to move the profiles of said dies into frictionalengagement with the blank in said first holder and means for releasablylocking said dies against rotation under the action of said resilientmeans, said machine tool having a trip arranged to deactivate saidlocking means in response to movement of said one holder to saidpredetermined position.

25. in a machine for rolling threads or analogous profiles into theperipheral surfaces of ductile round blanks, a combination comprising afirst holders arranged to support a blank therein; a head including asecond holder, a plurality of spaced-apart substantially cylindricaldies rotatably mounted in said second holder and having profilescomplementary to the desired profile of a blank in said first holder andflats which are adjacent to but spaced from a blank in said firstholder, and a gear train mounted in said second holder and connectngsaid dies for rotation in synchronism with each other, said gear trainincluding discrete first gears rigid with said dies and a second gearsurrounded by and meshing with said first gears, said head furthercomprising resilient means for rotating said dies about their axessufficiently to move the profiles of said dies into frictionalengagement with the blank in said first holder, and means for releasablylocking said dies against rotation under the action of said resilientmeans, said locking means comprising a projection on said second gear,first and second locking bolts movable into and from the path ofmovement of said projection, and actuating means for moving said bolts,one of said holders being movable relative to the other holder to apredetermined position in which said dies are adjacent to a selectedportion of the peripheral surface of a blank in said first holder andthe axes of said dies are disposed at identical distances from the axisof such blank; and means for rotating one of said holders about the axisof a blank in said first holder whereby the blank and the second holdermove relative to each other about the axis of the blank in said firstholder and the dies complete the profiling of the blank in response tocompletion of one revolution about their respective axes owing tofrictional engagement with the blank.

26. A combination as defined in claim 25, wherein said projectioncomprises a portion which is engaged by said first bolt before saidprojection is engaged by said second bolt, said locking means furthercomprising first and second springs for respectively biasing said firstand second bolts with a weaker and greater force toward engagement withthe projection of said second gear.

27. A combination as defined in claim 25, wherein said resilient meansengages and tends to rotate said second gear.

28. A combination as defined in claim 25, further comprising means formoving said dies radially of a blank in said first holder.

29. A combination as defined in claim 28, wherein said means for movingsaid dies radially comprises discrete stubs rotatably mounted in saidsecond holder and each having an eccentric portion rotatably supportinga die, third gears rigid with said stubs, and means for simultaneouslyrotating said third gears through identical angles.

30. A combination as defined in claim 29, wherein said means forrotating said third gears comprises a ring gear meshing with said thirdgears and being rotatable with respect to said second holder.

31. A combination as defined in claim 25, further comprising an annulartrip mounted on and rotatable with respect to said second holder tothereby disengage said bolts from said projection through the medium ofsaid actuating means.

1. A method of rolling threads or analogous profiles into the peripheralsurfaces of ductile round blank means with die means including aplurality of substantially cylindrical dies having profiles which arecomplementary to the desired profiles of blanks, comprising the steps ofpositioning the dies into frictional contact with the peripheral surfaceof a blank means while maintaining the axes of the dies at identicaldistances from the axis of the blank means; rotating one of said meansrelative to the other about the axis of the blank means so that the diesrotate about their respective axes due to frictional engagement with theblank means and complete the rolling of a profile into the peripheralsurface of the blank means in response to completion of one revolutionabout their respective axes; and biasing said dies to predeterminedangular positions which said dies assume upon disengagement of theirprofiles from a profiled blank means.
 2. A method of rolling threads oranalogous profiles into the peripheral surfaces of ductile round blankmeans with die means including a plurality of substantially cylindricaldies having profiles which are complementary to the desired profiles ofblanks, comprising the steps of positioning the dies into frictionalcontact with the peripheral surface of a blank means while maintainingthe axis of the dies at identical distances from the axis of the blankmeans; rotating one of said means relative to the other about the axisof the blank means so that the dies rotate about their respective axesdue to the frictional engagement with the blank means and complete therolling of a profile into the peripheral surface of the blank means inresponse to completion of one revolution about their respective axes;locking the dies against rotation about their respective axes prior tosaid positioning step; and locking said dies against rotation abouttheir respectivE axes upon completion of said one revolution.
 3. Amethod as defined in claim 2, further comprising the steps of moving ablank means into a predetermined position relative to the dies, or viceversa, and terminating the first locking step in the course of saidmoving step.
 4. A method as defined in claim 2, wherein said secondlocking step is effected in response to completion of said onerevolution.
 5. In a machine for rolling threads or analogous profilesinto the peripheral surfaces of ductile round blanks, a combinationcomprising a first holder arranged to support a blank therein; a headincluding a second holder, a plurality of spaced-apart substantiallycylindrical dies rotatably mounted in said second holder and havingprofiles complementary to the desired profile of a blank in said firstholder, a gear train mounted in said second holder and connecting saiddies for rotation in synchronism with each other, means for moving theaxes of said dies nearer to or away from each other and comprisng shaftsturnably mounted in said second holder and having eccentric portionssurrounded by the respective dies, one of said holders being movablerelative to the other holder to a predetermined position in which saiddies are adjacent to a selected portion of the peripheral surface of ablank in said first holder and the axes of said dies are disposed atidentical distances from the axis of such blank; and means for rotatingone of said holders about the axis of a blank in said first holderwhereby the blank and said second holder move relative to each otherabout the axis of the blank in said first holder and the dies completethe profiling of the blank in response to completion of one revolutionabout their respective axes owing to frictional engagement with theblank.
 6. A combination as defined in claim 5, wherein the profile ofeach of said dies comprises a section whose radius increases contrary tothe direction of rotation of the die about its axis during frictionalengagement with a blank is said first holder.
 7. A combination asdefined in claim 6, wherein said radius increases gradually.
 8. Acombintion as defined in claim 6, wherein said section of the profile ofeach of said dies has raised portions of uniform height.
 9. Acombination as defined in claim 6, wherein said section of the profileof each of said dies has raised portions whose height increases contraryto the direction of rotation of the respective die about its axis.
 10. Acombination as defined in claim 9, wherein the profile of each of saiddies has a second section which follows the respective first mentionedsection, as considered contrary to the direction of rotation of thecorresponding die about its axis, and has a constant radius.
 11. Acombination as defined in claim 6, wherein the profile of each of saiddies has a flat which precedes said section, as considered in thedirection of rotation of the respective die about its axis, said flatbeing adjacent to and spaced from said selected portion of a blank insaid predetermined position of said one holder and said head furthercomprising means for rotating said dies about their respective axessufficiently to move said sections into frictional engagement with theblank in said first holder.
 12. A combination as defined in claim 5,wherein the profile of each of said dies has a first section whoseradius increases contrary to the direction of rotation of the respectivedie about its axis, a second section following said first section andhaving a constant radius, and a third section which follows said secondsection and whose radius decreases in said direction.
 13. A combinationas defined in claim 12, wherein each of said first sections extendsalong an arc of at least 180*, as considered in the circumferentialdirection of the respective die.
 14. A combination as defined in claim12, wherein each of said second sections extends along an arc ofapproximately 90*, as considered in the circumferential direction of therespective die.
 15. A combination as defined in claim 12, wherein eachof said third sections extends along an arc of less than 100*, asconsidered in the circumferential direction of the respective die. 16.In a machine for rolling threads or a nalogous profiles into theperipheral surfaces of ductile round blanks, a combination comprising afirst holder arranged to support a blank rotatable about its axis; ahead including a second holder, a plurality of spaced-apartsubstantially cylindrical dies rotatably mounted on said second holderand having profiles complementary to the desired profile of a blank insaid first holder, and a gear train mounted in said second holder andconnecting said dies for rotation in synchronism with each other, saidhead being movable relative to said first holder from a first to asecond position in which said dies are adjacent to a selected portion ofthe peripheral surface of a blank in said first holder and the axes ofsaid dies are disposed at identical distances from each other;releasable locking means for locking said dies, when said head is insaid first position, in a predetermined angular relationship withrespect to each other; means cooperating with said releasable lockingmeans to automatically release the latter upon movement of said headfrom said first to said second position; means operatively connected tosaid dies for moving the same out of said predetermined angular positionwhen said locking means are released so that the dies engage theperipheral surface of a blank in said first holder; and means forrotating said first holder about the axis of a blank in said firstholder whereby said blank rotates with said first holder and the diescomplete the profiling of the blank in response to completion of onerevolution about their respective axes owing to frictional engagementwith the blank.
 17. A combination as defined in claim 16, wherein eachof the dies has a flat, and wherein said flats are adjacent to butspaced from the peripheral surface of the blank in said predeterminedangular position of said dies.
 18. In a machine for rolling threads oranalogous profiles into the peripheral surfaces of ductile roung blanks,a combination comprising, a first holder arranged to support a blanktherein; a head including a second holder, first and second spaced-apartsubstantially cylindrical dies rotatably mounted in said second holderand having profiles complementary to the desired profile of the blank insaid first holder, and each of said dies having a flat, said headfurther comprising means for rotating said dies about their respectiveaxes to move the profiles of said dies in frictional engagement with theblank in said first holder, a gear train mounted in said second holderand connecting said dies for rotation in synchronism with each other,said gear train including first and second gears coaxial and rigid withsaid first and second dies, third and fourth gears respectively matingwith said first and second gears, and additional gear means mating withsaid third and fourth gears, and detent means for releasably holdingsaid dies against rotation about their respective axes, said detentmeans comprising first and second projections respectively provided onsaid third and fourth gears, first and second locking bolts movable intoand out of the path of movement of said first and second projections,and actuating means for moving said bolts, one of said holders beingmovable relative to said other holder to a predetermined position inwhich said flats are adjacent to a selected portion of the peripheralsurface of the blank in said first holder and the axes of said dies aredisposed at identical distances from the axis of such blank; and meansfor rotating one of said holders about the axis of a blank in said firstholder whereby the blank and the second holder move relative to eachother about the axis of the blank in said first holder and the diescomPlete the profiling of the blank in response to completion of onerevolution about their respective axes owing to frictional engagementwith the blank.
 19. A combination as defined in claim 18, wherein saiddetent means further comprises discrete first and second resilient meansfor biasing said first and second locking bolts into the path ofmovement of the respective projections.
 20. A combination as defined inclaim 19, wherein the bias of said first resilient means exceeds thebias of said second resilient means and said actuating means is arrangedto disengage one of said bolts from the respective projection when theother of said bolts extends into the path of movement of the respectiveprojection whereby said first resilient means automatically disengagessaid second bolt against the opposition of said second biasing meanswhen said actuating means allows said first bolt to move into the pathof movement of said first projection.
 21. A combination as defined inclaim 20, wherein said second locking bolt is mounted in said secondholder with limited freedom of movement relative to said actuatingmeans.
 22. A combination as defined in claim 18, wherein said additionalgear means comprises a fifth gear in mesh with said third and fourthgears and said means for rotating said dies comprises resilient meansarranged to bias said fifth gear so that said fifth gear tends to rotatesaid dies by way of said first to fourth gears when said detent meanspermits rotation of said third and fourth gears, said resilient meansbeing arranged to bias said projections against the respective lockingbolts when said flats are adjacent to but spaced from a blank in saidfirst holder.
 23. A combination as defined in claim 22, wherein saidfifth gear comprises an eccentric post and said resilient meanscomprises a spring connected to said post and reacting against saidsecond holder.
 24. In a machine for rolling threads or analogousprofiles into the peripheral surfaces of ductile round blanks, acombination comprising a first holder arranged to support a blanktherein; a head including a second holder, a plurality of spaced-apartsubstantially cylindrical dies rotatably mounted in said second holderand having profiles complementary to the desired profile of a blank insaid first holder, and a gear train mounted in said second holder andconnecting said dies for rotation in synchronism with each other, one ofsaid holders being movable relative to the other holder to apredetermined position in which said dies are adjacent to a selectedportion of the peripheral surface of a blank in said first holder andthe axes of said dies are disposed at identical distances from the axisof such blank; and a machine tool for rotating one of said holders aboutthe axis of a blank in said first holder whereby the blank and thesecond holder move relative to each other about the axis of the blank insaid first holder and the dies complete the profiling of the blank inresponse to completion of one revolution about their respective axesowing to frictional engagement with the blank, said dies having flatswhich are adjacent to but spaced from the blank in said first holder insaid predetermined position of said one holder, and said head furthercomprising resilient means for rotating said dies about their respectiveaxes sufficiently to move the profiles of said dies into frictionalengagement with the blank in said first holder and means for releasablylocking said dies against rotation under the action of said resilientmeans, said machine tool having a trip arranged to deactivate saidlocking means in response to movement of said one holder to saidpredetermined position.
 25. In a machine for rolling threads oranalogous profiles into the peripheral surfaces of ductile round blanks,a combination comprising a first holders arranged to support a blanktherein; a head including a second holder, a plurality of spaced-apartsubstantially cylindrical dies rotatably mounted in saiD second holderand having profiles complementary to the desired profile of a blank insaid first holder and flats which are adjacent to but spaced from ablank in said first holder, and a gear train mounted in said secondholder and connectng said dies for rotation in synchronism with eachother, said gear train including discrete first gears rigid with saiddies and a second gear surrounded by and meshing with said first gears,said head further comprising resilient means for rotating said diesabout their axes sufficiently to move the profiles of said dies intofrictional engagement with the blank in said first holder, and means forreleasably locking said dies against rotation under the action of saidresilient means, said locking means comprising a projection on saidsecond gear, first and second locking bolts movable into and from thepath of movement of said projection, and actuating means for moving saidbolts, one of said holders being movable relative to the other holder toa predetermined position in which said dies are adjacent to a selectedportion of the peripheral surface of a blank in said first holder andthe axes of said dies are disposed at identical distances from the axisof such blank; and means for rotating one of said holders about the axisof a blank in said first holder whereby the blank and the second holdermove relative to each other about the axis of the blank in said firstholder and the dies complete the profiling of the blank in response tocompletion of one revolution about their respective axes owing tofrictional engagement with the blank.
 26. A combination as defined inclaim 25, wherein said projection comprises a portion which is engagedby said first bolt before said projection is engaged by said secondbolt, said locking means further comprising first and second springs forrespectively biasing said first and second bolts with a weaker andgreater force toward engagement with the projection of said second gear.27. A combination as defined in claim 25, wherein said resilient meansengages and tends to rotate said second gear.
 28. A combination asdefined in claim 25, further comprising means for moving said diesradially of a blank in said first holder.
 29. A combination as definedin claim 28, wherein said means for moving said dies radially comprisesdiscrete stubs rotatably mounted in said second holder and each havingan eccentric portion rotatably supporting a die, third gears rigid withsaid stubs, and means for simultaneously rotating said third gearsthrough identical angles.
 30. A combination as defined in claim 29,wherein said means for rotating said third gears comprises a ring gearmeshing with said third gears and being rotatable with respect to saidsecond holder.
 31. A combination as defined in claim 25, furthercomprising an annular trip mounted on and rotatable with respect to saidsecond holder to thereby disengage said bolts from said projectionthrough the medium of said actuating means.